The morphogenesis and cell wall composition of the trichome and its function in response to salt and retaining condensed water in halophyte Salsola ferganica

Desert plants have evolved different strategies to cope with the harsh environmental conditions. Trichomes are defensive epidermal protrusion of many plants, which provide a model to gain insight into the control of cell fate and morphogenesis. S. ferganica , a desert halophyte, develops thick, long trichomes on true leaf in seedling stage to ensure its survival. In the present study, we investigated the trichome on the morphogenesis along with related gene expression, the cell wall composition, and the preliminary function in salt accumulation and maintenance of the condensed water as well, results revealed that the trichome of S. ferganica was initiated from the epidermal primordium followed by two to three times of cell division to form a multicellular trichome, which was affected by abiotic stress; meanwhile, some genes associated with trichome development were positively involved. Analysis of cell wall composition showed that different polysaccharides including heavily methyl-esterified and fully de-esterified pectins (before maturation, probably in the primary wall), xyloglucans (in the middle early and middle stages, probably in the secondary wall), and extension proteins (during whole developmental period) were detected, which were different from trichomes of Arabidopsis and cotton. Moreover, trichomes presented functions to accumulate salt from the mesophyll cell and secrete it to the outer space; and retain larger amount of the condensed water in the complex web system formed by the thick, long hairs. Our findings should contribute to further understanding of the biogenesis and functions of plant accessory structures such as trichomes in deserts plants.